The Vendorians are a sapient extraterrestrial species with the ability to reshape their molecular and even atomic structure almost at will, being able to assume any form with similar size and mass. On their natural form, they are radially-symmetrical beings with six tentacles and six yellow eyes symmetrically arranged around the head, giving them a 360 degrees visual field.
Their home planet, Vendor, is located between Federation and Romulan territory, in the Neutral Zone. Given the Vendorians' transforming abilities and love of deception, their planet has been quarantined by a mutual agreement between the two powers to prevent the use of Vendorian spies.
Vendorians also have the ability to render humanoids temporarily unconscious by touch. Their shapeshifting allows them to imitate even fingerprints and vocal signatures, and presumably brain patterns as well, since spending too much time imitating another lifeform will cause the Vendorian to start experiencing the same thoughts and emotions of the being they are mimicking, which effectively becomes part of them in the long run.